Switzerland is easily accessible by air. From the airports, there is good public transport to most of the trailheads.
The Lake District can be reached via hub airports such as Liverpool, Manchester or Leeds. From there you can continue with public transport.
Norway has a variety of local airports from where to continue with local transport. Examples are Bodo or Lekness.
From wherever you travel, NatuurGeweldig will provide you with useful information.